Fix a logging NPE problem

bug:6864064
Change-Id: I3237e55cb164462b9616515b0de009bf687f1dca

Author: Robert Greenwalt

telephony/java/com/android/internal/telephony/cdma/CdmaServiceStateTracker.java

@@ -1378,7 +1378,8 @@ void setTimeFromNITZString (String nitz, long nitzReceiveTime)
                 mZoneTime    = c.getTimeInMillis();
             }
             if (DBG) {
-                log("NITZ: tzOffset=" + tzOffset + " dst=" + dst + " zone=" + zone.getID() +
+                log("NITZ: tzOffset=" + tzOffset + " dst=" + dst + " zone=" +
+                        (zone!=null ? zone.getID() : "NULL") +
                         " iso=" + iso + " mGotCountryCode=" + mGotCountryCode +
                         " mNeedFixZone=" + mNeedFixZone);
             }